(1) Field of the Invention
This invention relates to a tool head for use in machine tools. More particularly, the present invention relates to a tool head of an improved type for improving the locating accuracy of cutting insert holders.
(2) Description of the Prior Art
There has conventionally been known a tool head which is equipped with plural cutting insert holders and is capable of simultaneously adjusting the positions of these plural cutting insert holders by means of a single adjusting mechanism.
Screws are employed for the delivery of the above-mentioned cutting insert holders. Namely, the screws are rotated by a handle provided with calibration so that the cutting insert holders are fed by a pitch corresponding to the angle of rotation.
In the tool head of this kind, however, it has been difficult to furnish the feed screws for feeding the cutting insert holders with the same pitch. Consequently, variance of a moving distance occurs for each cutting insert holder fed in accordance with the angle of rotation of the handle. This phenomenon is not a critical problem during rough machining, but non-uniformity of the pitch of the feed screws exerts significant influences upon the machined surface during percision machining because adjustment of the cutting insert positions must be made on the order of microns in such a case. To solve this problem, accuracy of the feed screws may as well be improved, in principle. However, it is virtually not possible to realize the same pitch for a plurality of feed screws. On the other side, the attempt of improving the accuracy of the screw pitch in order to reduce the pitch error would result in the remarkable increase in the cost of production and hence, is not feasible in practice.